1. Field of the Invention
The present invention relates to methods for dicing wafers and particularly relates to methods for dicing wafers having semiconductor element sections arranged thereon to separate the semiconductor element sections. The present invention more particularly relates to a method for dicing a wafer having openings arranged in a face thereof and a dicing tape affixed to the wafer face to manufacture element substrates for liquid-discharging heads for discharging liquid from orifices arranged on the front faces of the substrates, the liquid being supplied from supply ports placed on the rear faces of the substrates. The present invention also relates to a method for manufacturing a liquid-discharging head using the dicing method.
2. Description of the Related Art
In general, various semiconductor elements are manufactured by the following procedure: a plurality of semiconductor circuit sections are simultaneously formed on a silicon wafer or other wafer types, the circuit sections are separated from each other in a dicing step, and then processed into sealed packages.
With reference to FIG. 26A, in such a dicing step, a wafer 101 having a plurality of element sections 101a arranged on the front face thereof is mounted on a dicing tape 110 affixed to a dicing frame K such that the rear face of the wafer 101 is in contact with the dicing tape 110. The dicing tape 110 includes a backing 111 and an adhesive 112, placed on the backing 111, for retaining the wafer 101.
The dicing tape 110 is a sheet including an adhesive and a backing coated therewith. The adhesive 112 contains an ultraviolet-curable compound such that the element sections 101a separated can be readily picked up individually by reducing the adhesive strength of the adhesive in a step subsequent to the dicing step.
The resulting dicing frame K is fixed on a chuck table of a dicing machine and the alignment of the wafer 101 is performed with an alignment device. As shown in FIGS. 26A and 26B, the wafer 101 is cut along dicing streets 101b arranged on the wafer 101 using a dicing blade B.
The diced wafer 101 is removed from the dicing machine and the rear face of the wafer 101 is irradiated with ultraviolet light, whereby the adhesive 112 is cured and thereby reduced in adhesive strength. This allows the separated element sections 101a to be readily peeled off from the dicing tape 110 and then separately picked up.
Since the element sections 101a of the wafer 101 are used as element substrates for liquid-discharging heads, nozzle layers 102 having orifices 105 for discharging liquid are arranged on the front face of the wafer 101 and ink supply ports 103 for supplying ink to the orifices 105 are each arranged under the corresponding nozzle layers 102. Each ink supply port 103 communicates with the corresponding orifice 105 with channels 104 placed therebetween, the channels 104 being arranged in the nozzle layers 102 (see Japanese Patent Laid-Open No. 11-179926, corresponding to U.S. Pat. No. 6,305,080).
Japanese Patent Laid-Open No. 62-79649 discloses that in order to enhance the efficiency of a dicing step by preventing problems such as insulation faults caused by the adhesion of an adhesive of a dicing tape to a dicing blade from occurring, the adhesive is partly cured along dicing streets before dicing is conducted.
Japanese Patent Laid-Open No. 11-111162 discloses that when a protective tape including an adhesive is affixed to the front face of a wafer and the wafer is then diced, portions of the adhesive that correspond to electrode sections (emitter regions) arranged on the wafer are cured in a step conducted prior to the step of affixing the protective tape to the wafer such that the adhesive is prevented from adhering to the electrode sections. However, this technique has a problem in that alignment must be performed before the protective tape is affixed to the wafer, increasing the number of manufacturing steps.
With reference to FIG. 27, since the wafer 101 has the element sections 101a having the ink supply ports 103 arranged under the element sections 101a, the adhesive 112 of the dicing tape 110 affixed to the rear face of the wafer 101 is exposed in the ink supply ports 103.
Therefore, when the wafer 101 is diced with the dicing blade B, the adhesive 112 is partly broken due to micro-vibration indicated by Arrow S during dicing as shown in FIG. 28B to create adhesive particles 112a, because the adhesive 112 contains the ultraviolet-curable compound and is therefore soft. The adhesive 112 is particularly soft when it contains an ultraviolet-curable acrylic compound. The adhesive particles 112a adhere to the edges of the ink supply ports 103 that are openings arranged under the element sections 101a as shown in FIG. 28B. Furthermore, cooling water W enters the orifices 105 of the nozzle layers 102 during dicing to make contact with the adhesive 112 partly exposed in the ink supply ports 103.
As shown in FIG. 29A, the cooling water W in the orifices 105 is then removed from the orifices 105 by air blowing. In this operation, as shown in FIG. 29B, pieces 112a are removed from the adhesive 112 partly exposed in the ink supply ports 103 because the adhesive 112 receives shock from air and the cooling water W. Although most of the removed adhesive particles 112a are discharged out of the nozzle layers 102 together with the cooling water W, a small amount of the adhesive particles 112a cannot be removed and therefore remain around the orifices 105.
It is known that a low-molecular weight component is eluted from the adhesive 112 into pure water although the amount of the eluted component is small. The eluted component as well as the adhesive particles 112a remains around the orifices 105 in some cases.
After the dicing tape 110 affixed to the rear face of the wafer 101 is irradiated with ultraviolet light and the adhesive strength of the adhesive 112 is thereby reduced, the element sections 101a separated from each other by dicing are removed from the dicing tape 110 and then picked up. The adhesive particles 112a present around the orifices 105 remain as they are after pickup is performed. Furthermore, the adhesive particles 112a probably remain as they are after the element sections 101a used as elements are subjected to a step subsequent to a mounting step. This causes the following problems: the adhesive particles 112a remaining in the element sections 101a cause a failure in discharging droplets from liquid-discharging heads and the adhesive particles 112a are dispersed in ink to block the orifices 105.